To replace the burnt-out bulb of the dipped beam on a Piaggio Vespa, remove the cover by unscrewing the 4 lower bolts. Lift the cover (without removing it as it is connected to the speedometer). Now, there are two screws on the sides of the headlamp, internally, plus the adjustment screw underneath. Unscrew them, and now the headlamp is only held by the electrical connections. The YouTuber recommends not disconnecting the headlamp but just removing the bulb holder, so you can easily access the bulb. Take this opportunity to lubricate the throttle and gearbox gears with WD-40. Also, check the position light bulb while you're at it. Replace the bulb (the YouTuber handles it correctly with gloves this time). Before refitting the reflector, clean it thoroughly, as internal dust reduces brightness. Refit the bulb into the reflector, reconnect the electrical connectors, and reassemble the headlamp inside the cover. Replace the internal screws and then the external ones. Now adjust the height. Refit the lower bolt used for adjustment - which you removed - following Piaggio's instructions. If you have some space available, do as our YouTuber suggests: make two marks with chalk, one on the ground and one on a wall, for reference, and adjust the headlamp height using the adjustment bolt located under the headlamp. At that point, you can tighten it.